Disclosed herein is a coating for a front face of an ink jet printhead. More particularly, disclosed herein is a coating that prevents wetting, drooling, and flooding of ultra-violet gel ink and solid ink on an ink jet printhead front face.
Fluid ink jet systems typically include one or more printheads having a plurality of ink jets from which drops of fluid are ejected towards a recording medium. The ink jets of a printhead receive ink from an ink supply chamber or manifold in the printhead which, in turn, receives ink from a source, such as a melted ink reservoir or an ink cartridge. Each ink jet includes a channel having one end in fluid communication with the ink supply manifold. The other end of the ink channel has an orifice or nozzle for ejecting drops of ink. The nozzles of the ink jets may be formed in an aperture or nozzle plate that has openings corresponding to the nozzles of the ink jets. During operation, drop ejecting signals activate actuators in the ink jets to expel drops of fluid from the ink jet nozzles onto the recording medium. By selectively activating the actuators of the ink jets to eject drops as the recording medium and/or printhead assembly are moved relative to one another, the deposited drops can be precisely patterned to form particular text and graphic images on the recording medium. An example of a full width array printhead is described in U.S. Patent Publication 20090046125, which is hereby incorporated by reference herein in its entirety. An example of an ultra-violet curable gel ink which can be jetted in such a printhead is described in U.S. Patent Publication 20070123606, which is hereby incorporated by reference herein in its entirety. An example of a solid ink which can be jetted in such a printhead is the Xerox Color Qube™ cyan solid ink available from Xerox Corporation.
One difficulty faced by fluid ink jet systems is wetting, drooling or flooding of inks onto the printhead front face. Such contamination of the printhead front face can cause or contribute to blocking of the ink jet nozzles and channels, which alone or in combination with the wetted, contaminated front face, can cause or contribute to non-firing or missing drops, undersized or otherwise wrong-sized drops, satellites, or misdirected drops on the recording medium and thus result in degraded print quality. Current printhead front face coatings are typically sputtered polytetrafluoroethylene coatings. When the printhead is tilted, the UV gel ink at a temperature of about 75° C. (75° C. being a typical jetting temperature for UV gel ink) and the solid ink at a temperature of about 105° C. (105° C. being a typical jetting temperature for solid ink) do not readily slide on the printhead front face surface. Rather, these inks flow along the printhead front face and leave an ink film which can interfere with jetting. For this reason, the front faces of UV and solid ink printheads are prone to wetting by the UV and solid inks. FIG. 1 is a photograph of a printhead front face after a printing run showing wetting and contamination of a UV gel ink over most of the nozzle area of the front face.
Maintenance procedures have been implemented in ink jet printers for preventing and clearing ink jet blockages and for cleaning the print head front face. A maintenance procedure for ink jet printers is described in U.S. Patent Publication 20080316247, which is hereby incorporated by reference in its entirety. Examples of maintenance procedures include jetting or purging ink from the ink jet channels and nozzles and wiping the printhead front face. Jetting procedures typically involve ejecting a plurality of drops from each ink jet in order to clear contaminants from the jets. Purging procedures typically involve applying an air pressure pulse to the ink reservoir to cause ink flow from all of the jets. The jetted ink may be collected in a waste reservoir such as a spittoon. The purged ink may be collected in a waste reservoir such as a waster tray. A wetted, contaminated printhead front face interferes with the collecting of the purged ink by preventing or reducing the ability of the ink to slide over the front face into the waste reservoir. Wiping procedures are usually performed by a wiper blade that moves relative to the nozzle plate to remove ink residue, as well as any paper, dust, or other debris that has collected on the print head front face. An example of a wiper assembly is described in U.S. Pat. No. 5,432,539, which is hereby incorporated by reference herein in its entirety. Jetting/purging and wiping procedures may each be performed alone or in conjunction with one another. For example, a wiping procedure may be performed after ink is purged through the jets in order to wipe excess ink from the nozzle plate.
Currently available coatings for ink jet printhead front faces are suitable for their intended purposes. However a need remains for an improved printhead front face coating that reduces or eliminates wetting, drooling, or flooding of UV or solid ink over the printhead front face. There further remains a need for an improved printhead front face coating that is robust to withstand maintenance procedures such as wiping of the printhead front face.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.